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December 31, 2016 22:28
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Snow Flake Demo With HTML5 Canvas And JavaScript
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<!DOCTYPE html> | |
<html> | |
<head> | |
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> | |
<title>HTML5 Canvas Snowflakes Demo</title> | |
<style> | |
html, body { | |
overflow: hidden; | |
} | |
</style> | |
</head> | |
<body onload="doTimer()" onresize="resizeCanvas()"> | |
<canvas id="mainCanvas"> | |
</canvas> | |
<script> | |
<!-- Written by Levent Divilioglu --> | |
<!-- 1.1.2017 --> | |
(function () { | |
canvas = document.getElementById('mainCanvas'); | |
ctx = canvas.getContext("2d"); | |
canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; | |
canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight; | |
WIDTH = canvas.width; | |
HEIGHT = canvas.height; | |
BLACK = "black"; | |
WHITE = "white"; | |
BLUE = "blue"; | |
clearScreen(); | |
VELOCITY_MIN = 4; | |
VELOCITY_MAX = 10; | |
phase = 0; | |
previousTimestamp = 0; | |
MAX_R = 4; | |
NUMBER_OF_SNOW_FLAKES = 500; | |
snowFlakes = generateSnowFlakes(NUMBER_OF_SNOW_FLAKES); | |
})(); | |
function resizeCanvas() { | |
canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; | |
canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight; | |
WIDTH = canvas.width; | |
HEIGHT = canvas.height; | |
} | |
function generateSnowFlakes(num) { | |
var snowFlakes = []; | |
for(var i = 0; i < num; i++) { | |
snowFlakes.push( { "index": i, "r": Math.random()*MAX_R, "x": Math.random()*WIDTH, "y": 0, "v_x": 0, "v_y": getRandom(VELOCITY_MIN,VELOCITY_MAX)} ); | |
} | |
return snowFlakes; | |
} | |
function handleSnowFlakes() { | |
for(var i = 0; i < snowFlakes.length; i++) { | |
if( (snowFlakes[i].y + snowFlakes[i].r) >= HEIGHT ) { | |
snowFlakes[i].y = 0; | |
snowFlakes[i].r = Math.random()*MAX_R; | |
snowFlakes[i].x = Math.random()*WIDTH; | |
snowFlakes[i].v_y = getRandom(VELOCITY_MIN,VELOCITY_MAX); | |
} else { | |
snowFlakes[i].y += snowFlakes[i].v_y; | |
snowFlakes[i].x += snowFlakes[i].v_x; | |
} | |
} | |
} | |
function drawSnowFlakes() { | |
for(var i = 0; i < snowFlakes.length; i++) { | |
ctx.beginPath(); | |
ctx.fillStyle = "rgba(255, 255, 255, " + (1.0 - (snowFlakes[i].y / 600.0)) + ")"; | |
ctx.arc(snowFlakes[i].x + snowFlakes[i].r, snowFlakes[i].y + snowFlakes[i].r, snowFlakes[i].r, 0, 2 * Math.PI, false); | |
ctx.fill(); | |
} | |
} | |
function animate(timestamp) { | |
timedelta = timestamp - previousTimestamp; | |
previousTimestamp = timestamp; | |
clearScreen(); | |
handleSnowFlakes(); | |
drawSnowFlakes(); | |
requestAnimationFrame(animate); | |
} | |
function clearScreen() { | |
var grd = ctx.createLinearGradient(0,0,0,HEIGHT); | |
grd.addColorStop(0,"#000000"); | |
grd.addColorStop(1,"#0000A0"); | |
ctx.fillStyle = grd; | |
ctx.fillRect( 0, 0, WIDTH, HEIGHT ); | |
ctx.fillStyle = "#FFFFFF"; | |
ctx.font = "180px Verdana"; | |
var text = "2017"; | |
var len = ctx.measureText(text).width; | |
ctx.fillText(text, WIDTH/2-len/2, HEIGHT/2 + 240/3); | |
} | |
function doTimer() { | |
window.requestAnimationFrame(animate); | |
} | |
function getRandom(a,b) { | |
return a + Math.random()*(b-a); | |
} | |
</script> | |
</body> | |
</html> |
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Here is a sample screen shot;